关于 List list = new ArrayList(int initialCapacity)

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maqian 2023-05-10 14:46:14 博主文章分类：java ©著作权

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List list = new ArrayList(int initialCapacity); //构造一个初始容量为initialCapacity的空列表。    
Sysout.out.println(list.size()); //size()方法指的是List中实际存放有多少个元素，故这里是0

API中对ArrayList构造函数的解释：

ArrayList的部分源代码:

/**   
* Constructs an empty list with the specified initial capacity.   
*   
* @param initialCapacity the initial capacity of the list.   
* @exception IllegalArgumentException if the specified initial capacity   
* is negative   
*/    
public ArrayList(int initialCapacity) {    
super();    
if (initialCapacity < 0)    
throw new IllegalArgumentException("Illegal Capacity: "+    
initialCapacity);    
this.elementData = (E[])new Object[initialCapacity];    
}    

/**   
* Constructs an empty list with an initial capacity of ten.   
*/    
public ArrayList() {    
// 注意这里。默认长度为10。这回知道了吧   
this(10);    
}   

/** 
* Constructs an empty list with the specified initial capacity. 
* 
* @param initialCapacity the initial capacity of the list. 
* @exception IllegalArgumentException if the specified initial capacity 
* is negative 
*/ 
public ArrayList(int initialCapacity) { 
super(); 
if (initialCapacity < 0) 
throw new IllegalArgumentException("Illegal Capacity: "+ 
initialCapacity); 
this.elementData = (E[])new Object[initialCapacity]; 
} 

/** 
* Constructs an empty list with an initial capacity of ten. 
*/ 
public ArrayList() { 
// 注意这里。默认长度为10。这回知道了吧
this(10); 
}